Dynamic parameters of a RC building extracted from earthquake data using the Random Decrement Technique

Abstract

The paper presents results from a study on monitoring the long-term variation of the dynamic characteristics of an 11-story reinforced concrete building located near Bucharest. Since the deployment, in December 2013, of a permanent monitoring system, 89 seismic events with a moment-magnitude (MW) larger than 3.8 were reported. Out of these, 80 were recorded properly by the seismic sensors and the data was used to extract the fundamental frequency and the damping ratio of the building for each event. The main method used to compute the dynamic parameters was the Random Decrement Technique. A dependency of the resulting fundamental frequencies on the maximum accelerations at the base and on top of the building was observed. Due to the structural peculiarities, the fundamental frequency of the building on the transverse direction was lower than the one on the longitudinal direction, this being reflected also by the experimental results. The maximum drop in the fundamental frequency was reported for the MW=5.5 October 28th, 2018 seismic event. By performing this type of analyses, the dynamic parameters of buildings can be tracked over long periods of time and their variation under seismic excitation can be assessed, allowing rapid detection of structural health alterations.